Ok. Guys. I understand it's not fun to hear you bought and promote the wrong cobs. As many show, 3500/4000k can be used for growing mj too. Like HPS, T5, fluo. No need to change them if you already bought the wrong ones. For grow led however, it's just wrong...
You should understand now why white cobs are mainly popular cannabis grow lights and pro horticulture lighting is still about blurple and white/red etc. And why Cree has the XPE leds specifically for horticulture. And why the pros are still using blurple or white/red etc. It should also start to sink in why I said white cobs suck (surely I've said that somewhere in one wording or the other lol). The truth is, not all white cobs suck for horticulture, the high cri (or even the lower color temps) are factually better.
Don't shoot the messenger...
View attachment 3697152
View attachment 3697151
Carotenoids is what makes plants look yellow-orange in fall. It absorbs the blue light, and when there is not a lot of chlorophyll to reflect green, and red is soaked up as usual, the color your eyes see are the yellow orange colors.
Carotenoids as well as the anthocyanin I mentioned and showed in graph earlier are so called accessory pigments. They absorb light and pass that on to chlorophyll indirectly. That comes with a cost, a big one too, especially if you run high blue in the first place. Understand what happens when anthocyanin malvidin builds up (your leaves turn blue-purple-red) on top of that.
"
Why the rate of Photosynthesis is higher in red light while the rate of absorption is highest of blue light?"
Blue light is absorbed not only by chlorophyll, but also by carotenoids, and some carotenoids are not in the chloroplasts; further, carotenes and xanthophylls make up the carotenoids.. and Carotenes do not transfer absorbed energy efficiently to chlorophyll, and thus some part of absorbed light in the blue is not going to photosynthesis. On the other hand, all of red light is absorbed by chlorophylls and used effectively.
Answered by
Prof. (Emiritus) Govindjee
Biochemistry, Biophysics and Plant
Biology,University of Illinois, 265 Morrill Hall,MC-116, 505 South Goodwin
Avenue, Urbana,IL 61801-3707, USA;
View attachment 3697164
Your cool white high blue cobs may seem efficient to you, they are
not for the plant. One of the reasons they 'work' should be obvious after our fine discussions on the effect temp has on photosynthesis...
View attachment 3697254 View attachment 3697255
Something you collectively choose to remain ignorant about too, but just like this won't be able to ignore it endlessly, and time is thus on my side.
Much of the blue light is just wasted and inefficient. Many of the blurple lights sucked because they were often not very efficient, and people rarely made up for the huge temp drop of the leaves and plant itself, and not because the concept is not valid. That would be like denying gravity. There is a difference between engineering grow lights and assembling bay lights in an energy-efficient as possible configuration.
As I mentioned before, blue for photomorphogenesis (light-regulated plant development), and red for assimilation.
Now, several people asked why then HPS with its low cri works so well. Well, because it has a very good spectrum for assimilation, opposed to your white cobs. Yes, sorry, it does. I think the fact they are designed by horticulturist for horticulture may have something to do with it...
View attachment 3697182
People are quick to say it's a horrible spectrum (and I didn't even pick the best...) but it's actually not bad at all. Especially considering it's not as easy as with LED. Not efficient, but very effective. Enough blue for photomorphogenesis, lots and lots of red and some FR too to produce. It's really the B, R, FR that matters here. The rest is not entirely useless but far less efficient, does not excite chlorophyll as much. In reality that white part of the graph is raised.
Anyone who has seen photos of HPS grows know the plants look yellow-ish. That's cause the red part is absorbed heavily, and the yellow light is absorbed very little, it is transmitted through leaves, and reflected from leaves. How and how much is extensively tested and depicted in graphs in one of the pdfs I posted. Contrary to excessive blue light, it does not have such adverse effects.
The low CRI in HPS is from the lack of non-orange-red light, it doesn't mean bad spectrum The lower CRI cobs are lower than the high CRI cobs because of the lack of red light, now that is a problem.
Any of you ever read the small notes in the cree led specs?
View attachment 3697191
lol at 7%... But look at the yellow note.
http://www.candleray.com/resources/led-lighting/new-color-quality-terminology-led-r9-value
"Assimilatieverlichting" is what HPS is used for in greenhouses. It's what we call it. Assimilation lighting... look it up lol... HPS is typically used instead of MH for hopefully now obvious reasons, which do not include efficiency as you think of efficiency.
Again, try to understand there are more important things than growing bud that fuels the proper research: "The realization that crop yields are reaching a plateau, while population increases continue at pace, has placed manipulation of photosynthesis..."
You are using the wrong cobs, blinded by efficiency at the source, refusing to learn and acknowledge the importance of botany. "Scientists don't know everything about plants, so scientists are in the dark" is just pure ignorance. While it turns out you actually have the option to employ two benefits of LED, lower energy consumption at the source, and lower energy consumption from producing less suboptimal light. At some point some fanboy or highpriest noticed the latest bin of the 3500 80cri has a higher output than the 3000K 80cri. Essentially supra's efficiency charts are for veg lights, skewing comparisons again. Build a proper one for flowering instead...
You're basically doing grow led all wrong, which is all a result of the cult behavior, the parroting and the inability to have a normal discussion and at least act like adults when someone disagrees with the Bibled. Anyone who buys or recommends 80cri 3500/4000K after this thread should simply admit for himself the attraction of cobs to him is to build an energy efficient light source, not a great or efficient grow light.
At the very least get the 3000K instead of 3500 or 4000 or even 5K. The difference between 3000K and 3500K is only half of the 17% difference between the 3500K 80 CRI and 3000K 90CRI. Next bin update it will be even less. You can build an efficient light with any. You can run max intensity with any. If you want to break the forum record or claim highest efficiency at the source for the lowest cost it makes sense to buy the 4000K 70cri, in any other case you pick the one with the best spectrum for plants.
Much of the gpw increase cob growers with let's say medium efficiency see is from a more efficient ppfd, heavily reduced reflector losses, and
despite the inappropriate (quite horrible) spectrum, even compared to HPS...
As I suggested before, do yourselves a favor, find a photobiologist or similar expert, a blogger, in a proper botany forum, or at a university. Tell him/her you are designing a grow light, present the spectrums and the output difference (without any skewing lol) and waste his/her time with such a silly question lol.
You're using the wrong cobs. Period.
